Any of the fast wireless chargers only charge 1.4 times faster than those that are regular chargers which are notoriously slow. You will always get the fastest charge with wall charging, but for overnight charging wireless charging of any kind is fine.
I have found that the free Samsung wireless charger runs warmer than another generic fast wireless charger without a fan.Why, I don't know. They both seem to charge at about the same speed. The difference is most noticeable when the phone is fully charged and sitting on the charger. The phone comes off the Samsung charger always warm, no matter how long it sits, whereas it is cool coming off the generic charger after it sits there fully charged for an hour.